Swift mutating

Swift 的 mutating 关键字修饰方法是为了能在该方法中修改 struct 或是 enum 的变量

protocol Person {
    mutating func changeName()
}

struct User: Person {
    var name = ""
    
    mutating func changeName() {
        name = "lisi"
    }
}

var user = User(name: "zhangsan")
//zhangsan
user.name
user.changeName()
//lisi
user.name